Explosive formation



March 11, 1969 ac, w n- JR ET AL EXPLOSIVE FORMATION Filed March a," 1966 l N VEN TORS GILBERT 6. WHITNEY, JR.

JOSEPH m SCI-070E051? TM -m ATTORNEY March 11, 1969 s. a. WHITNEY, 4a,, ETAL 3,431,763

EXPLOSIVE FORMATION File d March a. 1966 I N VEN TORS Y JOSE SCI-IROEDER W Am TM ATTORNEY Sheeimfl ofs GILEERT'C WHITNEY, JR.

March 11, 1969 G. c. WHITNEY, JR, ET AL 3,431,763

EXPLOSIVE FORMATION Filed March a, 1966 Sheet 3 of 5 INVENTORS GILBERT -C. WHITNEY, JR. Y JOSEPH M SCHROEDER A TT'ORNE) United States Patent 3,431,763 EXPLOSIVE FORMATION Gilbert C. Whitney, Jr., Dansville, N.Y., and Joseph W. Schroeder, Clark, N.J., assignors to Foster Wheeler Corporation, Livingston, N.J., a corporation of New York Filed Mar. 8, 1966, Ser. No. 532,647 US. CI. 72-56 Claims Int. Cl. B21d 26/08 ABSTRACT OF THE DISCLOSURE In explosive formation a covering layer of liquid transmitting medium is necessary to ensure that the effort of the explosion is properly directed into the material to be formed. To hold the liquid, either a heavy walled containment vessel or a light walled sealed dam around the material to be formed is utilized. With a light walled sealed dam, the dam must be rebuilt or at least rescaled after each detonation since the explosive force of the detonation causes damage to the dam. Rebuilding or resealing the dam, not only is time consuming, but also is costly. With a heavy walled containment vessel, the vessel is able to withstand the shock of detonation and can be repeated- 1y used without repair for multiple explosive formations. However, such a vessel is relatively large and expensive, and furthermore is cumbersome and impractical for forming very large objects with large charges. Other problems frequently encountered with explosive formation are objectionable noise levels developed during the detonation and scoring and severe abuse of the medium to be formed in the vicinity of the explosion; also, the liquid transmitting medium which is in contact with the explosive charges requires waterproof charges and charge holddown means such as cement or supports to retain the explosive in position.

Accordingly, it is an object of the present invention to provide a liquid transmitting medium containment means by which the above-mentioned problems are substantially solved and in which the explosive formation is substantially improved.

Therefore, the present invention provides a method for the explosive formation of a ductile material comprising the steps of, supporting the ductile material, disposing an explosive charge adjacent one side of the ductile material adjacent the portion of the ductile material to be formed, placing a flexible medium over said explosive charge, said flexible medium capable of holding a liquid transmitting medium therein, filling said flexible medium with a liquid transmitting medium, detonating the charge so as to create a force adjacent the portion of the ductile material to be formed thereby forming the portion of the material adjacent the charge. In a preferred form, although not limited thereto if other equivalent materials are available, the flexible medium comprises a plastic material such as polyethylene.

With this method of the present invention, the several problems mentioned above are substantially eliminated. Noise is diminished by the liquid transmitting medium containment of the present invention. An inexpensive disposable container is utilized; whereas with prior methods and systems, to reduce the noise to reasonable levels, and to properly direct the explosive force an excessively large darn or containment vessel was required, adding to the 3,431,763 Patented Mar. 11, 1969 expense. Further with the present invention a simple means of support is suflicient, over which, for example, a plastic sheet is draped to create a water pocket for holding the liquid. In this manner, a liquid sealing dam, or vessel, about the entire periphery of the plate to be formed, is completely eliminated. Moreover, the explosive charges do not contact the liquid, being under the flexible medium (or plastic sheet) which serves as a charge hold-down means. Accordingly, the charges are held in place by the weight of the liquid container thereabove and a small air pocket is created about the charges providing further improved results in the explosive formation.

In another method in accordance with the present invention, the flexible medium comprises a plastic bag or pillow case filled with the liquid transmitting medium which is placed over the charges prior todetonation. With this pillow, no bag or pillow support of any sort is required, the weight of the liquid therein serving to sufficiently hold the bag and likewise the explosive charges in place. To protect the material to be formed from local physical abuse and to provide further improved explosive formation, another bag filled with water is inserted between the explosive charges and the material to be formed.

Use of this process has been found economically successful for many uses, e.g., ash hopper seals, partition plates, etc., especially in cases where corrugations are desirable for strength or other purposes and where the normal use of cold forming equipment is uneconomical.

The invention and other objects and advantages thereof should become apparent from the following description of the invention in accordance with the drawings, in which:

FIGURE 1 illustrates free forming using a plastic sheet;

FIGURE 2 illustrates free forming using a plastic bag filled with water;

FIGURE 3 shows a free forming method utilizing two plastic bags;

FIGURE 4 demonstrates die formation with sheet explosive using a draped plastic sheet;

FIGURE 5 shows die formation with shaped charges and a plastic sheet;

FIGURE 6 illustrates die formation with a single plastic bag;

FIGURE 7 illustrates the same with two plastic bags;

FIGURE 8 illustrates die formation using shaped charges with two plastic bags;

FIGURE 9 and 10 show arrangements with the charges disposed respectively in a plastic sheet and a plastic bag;

FIGURE 11 shows a method for explosively forming extruded holes utilizing a plastic sheet for liquid containment; and

FIGURE 12 shows a combined bag and sheet arrangement using shaped charges.

Referring now to FIG. 1 for the explosive free forming of a ductile plate using a plastic sheet containment for the liquid transmitting medium. Ductile plate 11 to be formed into a corrugated sheet having two illustrative bends or ridges is supported at the ends by supports generally indicate at 13 fixed in the ground 15. Shaped explosive charges in the form of explosive prima cord strips 17 are supported on the plate adjacent the portions where it is desired to form the bends (or corrugations) in the plate. A plastic polyethylene sheet 19 is laid over the charges 17, and over the plate portions between the charges, and draped over sheet supports 21 (as shown at 23). The sheet supports 21 are higher than the charges 17 so that the plastic sheet forms a pocket or chamber 24 capable of holding a liquid medium, e.g., water 25, which completely covers the charges 17. The charges are then detonated by detonating means 27 to form the plate into the desired corrugations (indicated by the dashed lines 28 showing the plate 11 after the explosive formation). The supports 21, e.g., may be wood or wire mesh.

With this plastic containment sheet, liquid containment walls or seals are not required to hold the water as the pocket 24 formed by the plastic sheet provides the liquid containment means. The water within the pocket covering the charges reduces the noise level and aids focusing of the explosive forces against the plate by serving to a certain extent as a shield and reflector. There is an optimum height for the water. Increasing the water level (height) provides an improvement in the corrugation up to a certain water level beyond which any further increase in level decreases the depth of the corrugations. A small air pocket 29 is formed about the charges between the plate 11 and sheet of plastic 19 and is maintained sufficiently small by the weight of the liquid in the plastic sheet. This air pocket is believed to be advantageous for the explosive formation, and keeps the explosive dry during detonation, permitting the use of nonwaterproof explosive and eliminating the requirement for waterproof cementing of the explosive to the plate. Although not shown in the drawings, the plate may be clamped to the supports 13; however, the plastic sheet 19 is simply draped over the supports 21 and the weight of the water serves to hold the explosive charges and plate in position.

FIG. 2 shows the explosive formation of a ductile plate wherein the liquid is contained in a plastic polyethylene bag 30. Plate 11 is placed on the supports 13 and the explosive charges 17 are placed on the plate. Then the pillow case (bag) 30 is placed over the explosive and plate and then filled with water through a small slot 31 in the upper side of the bag, the slot 31 remaining open after filling the bag with water. The explosive charges are then dentonated to form the plate (as in FIG. 1).

Further advantages are achieved with this method. After filling the bag with water through slot 31 it is not necessary to seal the bag. No plastic support retaining means (such as end supports 21 of FIG. 1) is required for holding the plastic container, all plastic supports being completely eliminated. The bag 30 serves as a deformable hold-down means for the explosive and plate and as a liquid isolating means. Furthermore, as one explosion is occurring, the next plastic bag may be readied for placement in the explosive set-up, providing a saving in time greatly appreciated in mass production.

FIG. 3 and (FIGS. 7 and 8 to be hereinafter discussed) demonstrate the invention in a preferred form with an upper bag 32 and a lower bag 34, both filled with water 25. Between the bags are the explosive charges. The two bags 32, 34 are disposed above and adjacent to the plate portions to be corrugated. Lower bag 34 supports the charges 17 and usually has less liquid than the upper bag 32, the actual liquid levels and heights of the bags selected according to various parameters, such as, the quantity of explosive, the material and thickness of the plate 11, the desired depth and shape of the corrugations, the noise requirements, etc.

In accordance with the process illustrated by FIG. 3, the two plastic casings 32 and 34 are positioned and filled with fluid above the plate 11 to be formed. The explosive is positioned on the top of the lower bag in any desired configuration (in FIG. 3 are strips 17 to produce shape 28) prior to positioning above the plate and filling the lower bag to a desired fluid level. The upper bag is then positioned above the explosive and the lower bag and also filled to any desired level, generally to a greater level than that of the lower bag. All explosive material including the detonating cap (not shown) is completely covered, but isolated from the fluid in the upper plastic bag.

The advantages of this arrangement should be apparent. Noise level is substantially reduced. The explosive forces do not directly impact the plate. Local overstressing of the workpiece resulting from contact with explosive is completely eliminated. The depth of the corrugation for a given quantity of explosive is substantially increased over that obtained with the explosive directly against the plate. The material handling problem is greatly simplified because the explosive does not have to be fastened (or cemented) to and stored with a group of heavy plates for what may be an extended period of time prior to the actual explosive forming. Moreover, in addition to the other benefits discussed in connection with FIGS. 1 and 2, the lower bag 34 between the charges and the plate 11 provides an isolated liquid transmitting medium below the charges for transmitting the explosive forces from the charges to the plate with holding the charges in spaced relationship from the plate. This prevents scoring of the material, and other consequences, highly undesirable in certain types of metal formation. With the lower bag positioning, the explosive forces are radiated so that an enlarged circular Wave front 35 impacts the plate as a result of the spacing of the charge form the plate surface, permitting said enlarged corrugations and modified impact, as desired, for certain applications. The upper bag covers the charges with an isolated layer of liquid, and the weight of the liquid in the bags holds the charges and plate in postion without the necessity for hold-down means. Both bags sandwich the charges therebetween forming a sutficiently small air pocket 29 around the charges.

FIG. 4 and FIG. 5 show the invention practiced with backing dies 36, such as hard cast steel or any other suitable die material. A sheet of explosive or coating of explosive 38 (FIG. 4) or prima cord strips 17 (FIG. 5) are shown adjacent on the upper side of the plate 11. As in FIG. 1 a sheet of plastic 19 is draped over supports 21 which may extend from the explosive 38 (or placed on the plate 11 and strips 17 as shown in FIG. 5). The explosive when detonated by a detonator causes the plate 11 to form into the general configuration of the die. In other respects the process and advantages are the same as described above.

In FIG. 6 shaped explosive strips 17 as shown with a backing die 36. A single plastic bag 30 filled with water (as in FIG. 2) is utilized. The benefits achieved are similar to those explained in connection with FIG. 2. Although not shown, the single bag and die of FIG. 6 may also be used with sheet explosive instead of with shaped charges.

FIG. 7 shows the sheet explosive with die in a double bag arrangement similar to FIG. 3. With this arrangement, the explosive is disposed between the bags. Also shown in FIG. 7, although not restricted thereto, is a sand medium 40 into which the die is embedded for support during detonation and to prolong the life of the die. FIG. 8 illustrates a double bag arrangement and die with explosive strips 17 inserted between the bags directly above the corresponding die corrugations 42.

FIGS. 9 and 10 show arrangements where the explosive charges are disposed in contact with the liquid medium 25 (FIG. 9 showing the charges disposed within the plastic sheet pocket 24 and FIG. 10 showing the charges inside a single bag). With these arrangements, a single plastic containment may be utilized, and, it will be appreciated that, the liquid medium covers both the region above the charges and the region adjacent the plate and charges. Although FIGS. 9 and 10 show strip charges 17 without dies, it will be evident that use can be made with dies, or with dies and sheet explosive.

FIG. 11 shows that the invention may also be applied to the explosive formation of openings. A plastic sheet 19 is shown draped over supports 21 to create a pocket 24 which is filled with water 25. A back-up die ring 44 having an opening 46 provides space for the dissipation of the explosive force therethrough. The charges 47 are concentrated adjacent the opening (herein as a spiral strip) so as to produce an explosively formed plate 48 having a hole therein upon detonation. To achieve extruded edges 50, for example, for enabling the ready welding thereto of a nozzle (not shown) or other connections, the charges 47 are selected so as not to be excessive, yet suflicient to produce the extruded 'open ing. Although not shown, a single or double bag arrangement may also be used, with or without a backing die ring, to produce holes.

Table I illustrates the explosive forming as practiced by the invention. This table shows for various methods illustrated herein, types of plate to be formed; plate thickness; quantity of explosive used; water depth; average number of corrugations produced; and after forming depth of the corrugations.

2. A process for the explosive formation of a ductile material according to claim 1 wherein said flexible medium comprises a bag filled With the liquid transmitting medium, further comprising the step of orienting the ductile material in a substantially horizontal position, said bag being adjacent the upper side of the ductile material.

3. A process for the explosive formation of a ductile material into a desired shape according to claim 2 wherein said explosive charge is localized and shaped so as to explosively form the ductile material into the desired shape.

4. A process for the explosive formation of a ductile material according to claim 3 wherein the explosive TABLE I Type of plastic Plate Plate Prime No. Water Av. depth containment material thickness cord size corrudepth of corru- (steel) (gauge) (gr./1't.) gations (in.) gations (1n.)

11 60 4 3.0 5/8 11 60 4 2. O. 11 60 4 1 0. 5 11 60 4 1. 5 17/32 11 60 4 2.0 17/32 11 60 4 3.0 17/32 100 9 1. 5 5/8 10 100 9 2. 3/4 11 100 9 1. 75 11/16 D0 ..do 11 100 9 2. 25 3/16 Single bag Corten 14 100 4 3 5/8 Two bags do 14 50 4 5+ 1 Lower bag. 2 Upper bag.

Other arrangements are within the scope of the invention as will be apparent to those skilled in the art. For example, a two liquid layer containment may be utilized with a lower bag 34 between the explosive and plate, and a draped sheet with end supports 21 above the charges, instead of two 'bags (FIG. 12). Also, the shape of the material to be formed is not restricted, nor is the after detonation shape restricted to parallel corrugations, or even to corrugations, although indicated in that form in the illustrative examples. The use of plastic containers, which embody the inventive concept herein, may be used with explosive formation of any nature which would otherwise use a liquid transmitting medium notwithstanding the shapes of the objects to be formed thereby.

Free forming without backing dies illustrated by FIGS. 1-3, in which the explosive charges are shaped and localized so as to produce the desired product shape, is indicated in US. Patent No. 3,235,955 for Explosive Forming with Balanced Charges, which issued on Feb. 22, 1966, and US. Patent No. 3,372,565 for Contour Forming By Shaped Charges which issued on Mar. 12, 1968, with which the present invention may be utilized.

Although the invention has been described with respect to specific embodiments, many other variations within the spirit and scope of the invention as defined in the following claims will be apparent to those'skilled in the art.

What is claimed is:

1. A process for the explosive formation of a ductile material comprising the steps of:

supporting the ductile material,

placing an explosive charge on the ductile material,

disposing a flexible medium adjacent one side of the ductile material over said explosive charge, said flexible medium capable of shaping itself about the charge and holding a liquid transmitting medium therein,

filling the flexible medium with a liquid transmitting medium,

detonating the explosive charge to develop a shock wave of high kinetic energy so that a rapid strain is imparted to the portion of the ductile material to be formed thereby forming the portion of the ductile material adjacent the charge.

charge is contiguous to the ductile material, said bag shaping itself about the charge and the ductile material and covering the ductile material adjacent the charge.

5. A process for the explosive formation of a ductile material according to claim 4 wherein the bag is plastic.

6. A process for the explosive formation of a ductile material according to claim 5 wherein said explosive charge comprises a plurality of strips of explosive disposed in spaced relationship from each other for forming corrugations in the ductile material, said bag covering the explosive charge and ductile material portions therebetween.

7. A process for the explosive formation of a ductile material into a desired shape according to claim 2 further comprising the step of disposing a backing die adjacent the other side of the ductile material, said die formed substantially into the desired shape.

8. A process for the explosive formation of a ductile material into a desired shape according to claim 7 wherein said explosive charge is contiguous to the ductile material, said bag shaping itself about the charge and the ductile material and covering the ductile material adjacent the charge.

9. A process for the explosive formation of a ductile material into a desired shape according to claim 8 wherein said sheet is a polyethylene thermoplastic material, said explosive charge comprises a plurality of strips of explosive disposed in spaced relationship from each other for forming corrugations in the ductile material, said die having corresponding depressions therein adjacent the explosive strips, and said bag covering the explosive strips and ductile material portions therebetween.

10. A process for the. explosive formation of a ductile plate into a predetermined shape comprising the steps of:

supporting the ductile plate,

placing at least one explosive charge on said ductile plate,

disposing a layer of a flexible envelope over said explosive charge whereby said flexible envelope is capable of confining a liquid medium adapted to transmit force,

introducing said liquid medium into said flexible envelope such that said flexible envelope is shaped about the charge, and

detonating the explosive charge to develop a shock 3,160,949 12/1964 Bussey et al. 29-421 Wave of high kinetic energy so that a rapid strain 3,222,902 12/1965 Brejcha et al. 29-421 X is imparted to the portion of the ductile material to 3,238,753 3/1966 Benatar et al. 72-56 be formed thereby forming the portion of the ductile 3,242,939 3/ 1966 Fogg 29-421 X material adjacent the charge. 5 3,267,710 8/1966 Inoue 29421 X References Cited THQMAS H. EAGER, Primaly Examiner.

UNITED STATES PATENTS 2,379,149 3/1959 Brown 102 23 2,969,758 1/1961 Hewlett et al 29421 X 10 72-60;29421 3,060,879 10/1962 Staba 72-56 

